Microchannel cooler for high efficiency laser diode heat extraction

ABSTRACT

A laser diode package includes a laser diode, a cooler, and a metallization layer. The laser diode is used for converting electrical energy to optical energy. The cooler receives and routes a coolant from a cooling source via internal channels. The cooler includes a plurality of ceramic sheets and a highly thermally-conductive sheet. The ceramic sheets are fused together and the thermally-conductive sheet is attached to a top ceramic sheet of the plurality of ceramic sheets. The metallization layer has at least a portion on the thermally-conductive sheet. The portion is electrically coupled to the laser diode for conducting the electrical energy to the laser diode.

FIELD OF THE INVENTION

The present invention relates generally to laser diodes and, inparticular, to a cooling mechanism for a laser diode that providesimproved heat dissipation without requiring a deionized water coolant.

BACKGROUND OF THE INVENTION

Semiconductor laser diodes have numerous advantages. One advantage isthe small size of the laser diodes. For example, an active region of alaser diode has a width that is typically a submicron to a few microns,a height that is usually no more than a fraction of a millimeter, and alength that is typically less than about a millimeter. Internalreflective surfaces, which produce emission in one direction, are formedby cleaving the substrate from which the laser diodes are produced and,thus, have high mechanical stability.

High efficiencies are possible with semiconductor laser diodes with somehaving external quantum efficiencies near 70%. Semiconductor laserdiodes produce radiation at wavelengths from about 20 to about 0.7microns depending on the semiconductor alloy that is used. For example,laser diodes manufactured from gallium arsenide with aluminum doping(“AlGaAs”) emit radiation at approximately 0.8 microns (˜800 nm), whichis near the absorption spectrum of common solid state laser rods andslabs manufactured from Neodymium-doped, Yttrium-Aluminum Garnet(“Nd:YAG”), and other crystals and glasses. Thus, semiconductor laserdiodes can be used as an optical pumping source for larger, solid statelaser systems.

Universal utilization of semiconductor laser diodes has been restrictedby thermally related problems. These problems are associated with thelarge heat dissipation per unit area of the laser diodes that results inelevated junction temperatures and stresses induced by thermal cycling.Laser diode efficiency and the service life of the laser diode aredecreased as the operating temperature in the junction increases.

Furthermore, the emitted wavelength of a laser diode is a function ofits junction temperature. Thus, when a specific output wavelength isdesired, maintaining a constant junction temperature is essential. Forexample, AlGaAs laser diodes that are used to pump an Nd:YAG rod or slabshould emit radiation at about 808 nm because this is the wavelength atwhich optimum energy absorption exists in the Nd:YAG. However, for every3.5° C. to 4.0° C. deviation in the junction temperature of the AlGaAslaser diode, the wavelength shifts 1 nm. Accordingly, controlling thejunction temperature and, thus, properly dissipating the heat iscritical.

When solid state laser rods or slabs are pumped by laser diodes,dissipation of the heat becomes more problematic because it becomesnecessary to densely pack a plurality of individual diodes into arraysthat generate the required amounts of input power for the larger, solidstate laser rod or slab. However, when the packing density of theindividual laser diodes is increased, the space available for extractionof heat from the individual laser diodes decreases. This aggravates theproblem of heat extraction from the arrays of individual diodes.

One type of a cooling system for a laser diode package utilizesmicrochannel coolers made from metals, such as copper. These laser diodepackages are small, e.g., 1 mm thick, and have small water channelsrunning though them. The water channels pass close to a bottom side ofthe heat source (i.e., the laser diode bar), allowing for efficientthermal transfer. Because typical microchannel coolers are made fromcopper, electrical current and water coolant reside in the same physicalspace. Consequently, the coolant water must be deionized. However, theuse of deionized water requires all the parts that are exposed to thewater-supply to be either glass, plastic, stainless steel, orgold-plated. Parts that are not made of these materials usuallydeteriorate quickly due to erosion and corrosion problems. Accordingly,one problem associated with current microchannel coolers is that theyrequire a complicated and expensive deionized water system.

Thus, a need exists for a microchannel cooling system for a laser diodethat is electrically non-conductive and, preferably, has enhancedcharacteristics that reduce the adverse effects of the erosion and/orcorrosion problems described above. The present invention is directed tosatisfying one or more of these needs and to solving other problems.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a laser diode packageincludes a laser diode, a cooler, and a metallization layer. The laserdiode is used for converting electrical energy to optical energy. Thecooler receives and routes a coolant from a cooling source via internalchannels. The cooler includes a plurality of ceramic sheets and anexposed sheet. The ceramic sheets are fused together and the exposedsheet is attached to a top ceramic sheet of the plurality of ceramicsheets. The ceramic sheets are made of a material selected from thegroup consisting of low temperature cofired ceramics and hightemperature cofired ceramics. The metallization layer has at least aportion on the exposed sheet. The portion is electrically coupled to thelaser diode for conducting the electrical energy to the laser diode.

According to another aspect of the invention, a method of manufacturinga laser diode package includes providing a cooler comprised of theplurality of bonded ceramic sheets and a highly thermally-conductivesheet. The thermally-conductive sheet is bonded to a top ceramic sheetof the plurality of ceramic sheets. The method further includes applyinga metallization layer to the thermally-conductive sheet to which thelaser diode is attached.

In another embodiment, a laser diode package includes a laser diode, acooler, and a metallization layer. The laser diode is for convertingelectrical energy to optical energy. The cooler receives a coolant froma cooling source. The cooler includes a plurality of electricallynon-conductive sheets and an exposed sheet having a higher thermalconductivity than the plurality of sheets. The plurality of sheets arefused together and the exposed sheet is attached to a top sheet of theplurality of sheets. The cooler includes internal channels for routingthe coolant against a laser-diode mounting region on the exposed sheet.The metallization layer is located on the laser-diode mounting region ofthe exposed sheet. The laser-diode mounting region is electricallycoupled to the laser diode for conducting the electrical energy to thelaser diode.

According to yet another aspect of the invention, a laser diode arrayincludes a plurality of laser diode packages, as described above.

The above summary of the present invention is not intended to representeach embodiment or every aspect of the present invention. The detaileddescription and Figures will describe many of the embodiments andaspects of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings.

FIG. 1 illustrates a perspective view of a microchannel cooler for alaser diode, according to an embodiment of the present invention.

FIG. 2 illustrates an exploded view of the microchannel coolerillustrated in FIG. 1.

FIG. 3A illustrates a perspective view of a laser diode package,according to another embodiment of the present invention.

FIG. 3B illustrates an enlarged view of a portion of the laser diodepackage illustrated in FIG. 3A.

FIG. 4 illustrates an exploded perspective view of a plurality of laserdiode packages that create a laser diode array, according to analternative embodiment of the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. Itshould be understood, however, that the invention is not intended to belimited to the particular forms disclosed. Rather, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to FIG. 1, a microchannel cooler 10 includes a plurality ofsheets 12, each sheet 12 having an inlet hole 14, an outlet hole 16, andan alignment hole 18. The inlet hole 14 and the outlet hole 16 havegenerally the same diameter and shape, and are used, respectively, toreceive a coolant fluid from and return the coolant fluid to a coolingsource. The alignment hole 18 is centrally located between and has asmaller diameter than the inlet hole 14 and the outlet hole 16. Thealignment hole 18 is used to align the microchannel cooler 10 whenstacked with other microchannel coolers 10, as discussed below withrespect to FIG. 4. According to one embodiment, the microchannel cooler10 has a height (h) of 0.072 inches (1.829 millimeters), a width (w) of0.460 inches (11.684 millimeters), and a length (1) of 1.038 inches(26.365 millimeters).

As explained in more detail below, the microchannel cooler 10 functionsas a coolant manifold that is attached to a high-thermal conductivitymaterial (e.g., diamond) that, in turn, is in direct contact with alaser diode bar to be cooled with the coolant fluid. Because the sheetsof the microchannel cooler 10 are electrically non-conductive, themicrochannel cooler 10 provides thermal communication and electricalisolation between the laser diode bar and the coolant fluid. While theexamples described below specifically refer to a particular type ofmicrochannel cooler, it is understood that alternative embodiments ofthe microchannel cooler 10 include laminates of non-electricalconductors, semi-insulators, and high-resistivity materials.

Referring to FIG. 2, the plurality of sheets 12 includes nine sheets 12a-12 i. The first (or top or exposed) sheet 12 a preferably has a highthermal conductivity (e.g., diamond sheet) and the remaining eight lowersheets 12 b-12 i are low-temperature cofired ceramic (“LTCC”) sheets.When made of LTCC, the sheets 12 are bonded together in multiple layersby a thermal process that causes the glass molecules within the ceramicof each layer to bond together. After the sheets 12 b-12 i are bondedtogether, the top sheet 12 a and the bottom surface of the top ceramicsheet 12 b, which are metallized, are bonded together. Thismetallization is used to ensure a seal of the fluid openings around theinlet 14, the outlet 16, and an aperture 26 (FIG. 2) on the top ceramicsheet 12 b. Each of the sheets 12 b-12 i is processed to producedistinct internal channels (such as by punching or laser etching) sothat coolant channels are formed between the respective inlet hole 14and outlet hole 16 to allow the coolant fluid to pass through themicrochannel cooler 10.

In one example, the eight lower sheets 12 b-12 i are manufactured usinga “DuPont 951AX” LTCC material with a thickness of about ten mils (0.01inches). Alternatively, the eight lower sheets 12 b-12 i can be madeusing a high-temperature cofired ceramic material (“HTCC”).Alternatively yet, any of the plurality of sheets 12 can be made from amaterial selected from LTCC, HTCC, diamond, silicon carbide (SiC),aluminum nitride (AlN), cubic boron nitride (cBN), pyrex, silicon,sapphire, PEEK™ (Polyetheretherketone), beryllium oxide (BeO), glass,and other similar materials. The sheet material is selected based on itslow electrical conductivity characteristic, which is needed to preventthe mixing of the coolant and the electrical current.

The top sheet 12 a includes a laser diode area 20, which is located on atop surface of the top sheet 12 a and is generally a narrow strip. Thelaser diode area 20 is near a front side 22 (shown in FIG. 1) of themicrochannel cooler 10. In one example, the laser diode area 20 isapproximately 0.120 inches (3.048 millimeters). A metallic layer isapplied to the laser diode area 20 to create an electrically conductivearea for conducting electrical current to a laser diode bar (which isnot shown) that is mounted on the laser diode area 20. The metalliclayer is a solid, solderable metal (e.g., gold), for attaching the laserdiode bar. Alternatively, the metallic layer can be made using anyelectrically conductive material and/or their respective alloys,including gold, nickel, titanium, platinum, etc. The top surface of thetop sheet 12 a is preferably lapped and polished prior to applying themetallic layer. The front corner between the laser diode area 20 and thefront side 22 of the microchannel cooler 10 is typically made “square”with less than twenty-five micrometers, and, preferably, less than fivemicrometers of rounding.

The metallic layer is also applied along one or more of a front side 22and a pair of lateral sides 24 (shown in FIG. 1) of the microchannelcooler 10, and along a bottom surface of the bottom sheet 12 i. Themetallic layer can be applied to the entire surface area of a respectiveside or it can be applied only to a portion of the respective side. Forexample, the metallic layer can be applied to only a front portion of alateral side 24. The metallic layer is used to create an electrical pathfor conducting electricity from the bottom surface of the bottom sheet12 i to the laser diode bar that is mounted in the laser diode area 20of the top sheet 12 a.

Optionally, the metallic layer that is applied to the sides and/or thebottom surface of the microchannel cooler 10 can be different from themetallic layer that is applied to the laser diode area 20. For example,the metallic layer can be a nickel metal that is applied in the form ofa mesh. The dimensions of the metallic layer are optionally selectedsuch that a DC current of 100 amperes can flow to the laser diode barthat is mounted in the laser diode area 20 of the top sheet 12 a.

A number of the lower sheets 12 b-12 i include one or moremulti-directional apertures 26 in addition to the inlet hole 14, theoutlet hole 16, and the alignment hole 18. For example, the sheet 12 hadjacent to the bottom sheet 12 i includes a plurality of L-shapedapertures 26 near the front and lateral sides of the sheet 12 h, and aplurality of lateral apertures 26 connected to the inlet hole 14. Inaddition to the coolant fluid flowing in a direction parallel to theaxis of the inlet hole 14, the multi-directional apertures 26 are usedto distribute the flow of the coolant fluid in at least one otherdirection that is perpendicular to the axis of the inlet hole 14.Specifically, the multi-directional apertures 26 distribute the coolantfluid beneath the laser diode area 20 for a more efficient removal ofheat produced by the laser diode bar. The inlet 14 and outlet 16 havedimensions of about 3 mm to about 4 mm. The dimensions of larger ones ofthe apertures 26 are in range of about 1 to about 2 mm. The smallerperforations and apertures 26 in the sheets 12 e and 12 f, which areused for creating enhanced flow (e.g., turbulent flow) toward thebackside of the diode area 20 of the top sheet 12 a, have dimensionsthat are in the range of a few hundred microns. Arrows are shown toindicate the general direction of flow of the coolant fluid. AlthoughFIG. 2 illustrates one type of internal channel system in themicrochannel cooler 10, other types of channels and paths can be used.

Using a high thermally-conductive material, such as diamond or BeO, forthe top sheet 12 a increases heat removal performance of themicrochannel cooler 10. Further, the electrically non-conductive sheets12 a-12 i eliminate the need for using a typical complicated deionizedwater system. For example, the microchannel cooler 10 can use a simpledistilled water system or any other conductive coolant, such asFluoroinert® from the 3M Corporation.

Referring to FIGS. 3A and 3B, a laser diode package 30 includes themicrochannel cooler 10, a laser diode bar 32, an insulator substrate 34,and a spring 36. The laser diode package 30 can be used, as explained inmore detail in reference to FIG. 4, to stack a plurality of laser diodepackages 30 into an array. The laser diode bar 32 is mounted in thelaser diode area 20 such that an emitting surface 38 is positionedsubstantially flush with the front surface 22 of the microchannel cooler10.

The insulator substrate 34 is made from an electrical insulator, such asBeO. Optionally, the insulator substrate 34 includes a metallic layer onboth of its top and bottom surfaces. The metallic layer on the lowersurface is present to allow the insulator substrate 34 to be solderedonto the top sheet 12 a of the microchannel cooler 10. The metalliclayer on the upper surface is present to allow the insulator substrate34 to be soldered onto the spring 36. The spring 36 is metallic and ismounted to the laser diode bar 32 and the insulator substrate 34. Thespring 36 allows electrical contact to the adjacent layer diode package30, as shown in FIG. 4.

Referring to FIG. 4, a laser diode array 40 includes a top laser diodepackage 30 a and a bottom laser diode package 30 b, each of whichincludes respective spacer plates 42 a, 42 b and a respective pair ofO-rings 44 a, 44 b. Each spacer plate 42 a, 42 b is positioned generallyoverlapping the corresponding inlet hole 14 a, 14 b, outlet hole 16 a,16 b, and alignment hole 18 a, 18 b (not shown). Each spacer plate 42 a,42 b covers a portion of the entire surface area of the top sheet of therespective laser diode package 30 a, 30 b. Specifically, the spacerplate 42 a, 42 b covers the portion that is away from the spring 36 a,36 b.

The spacer plate 42 b on the bottom laser diode package 30 b isprimarily used for providing a location for the O-rings 44 b that areplaced over the inlet 14 b an the outlet 16 b. The spacer plate 42 bgenerally has a thickness that is about the same as the combinedthickness of the laser diode bar 32 and the spring 36 in FIG. 3 b. Inanother embodiment, the plate 42 b is unnecessary and it is replaced bygrooves in the top sheet 12 a that receive the O-ring 44 b. The samearrangements can be made in the top spacer plate 42 a.

The pairs of O-rings 44 a, 44 b are inserted into respective ones of theinlet hole 14 a, 14 b and outlet hole 16 a, 16 b to provide a leak-freepassage for the coolant fluid. For example, the pair of O-rings 44 bensure that the coolant fluid will not leak in the space located betweenthe top surface of the bottom spacer plate 42 b and the bottom surfaceof the top laser diode package 30 a.

The laser diode array 40 further includes a guide pin 46, a bottomcontact 48, and a bottom end cap 50. The guide pin 46 is secured to thebottom contact 48 and is inserted through corresponding alignment holes18 a, 18 b of the laser diode packages 30 a, 30 b. The bottom contact 48is located between the bottom laser diode package 30 b and the bottomend cap 50, from which the coolant fluid flows upwards via the inlethole 14. The bottom contact 48 includes a respective spring 36 c, arespective inlet hole 14 c, and a respective outlet hole 16 c. Thebottom contact 48 is electrically non-conductive, but includes anelectrically conductive coating for conducting current to the spring 36c.

The coolant fluid is passed to each of the laser diode packages 30 a, 30b via the respective inlet hole 14 a, 14 b and is returned to via therespective outlet hole 16 a, 16 b. An upper end cap (not shown) is usedto provide a cap to the inlet 14 and the outlet 16 on the uppermostlaser diode package 30. Thus, the inlets 14 of the laser diode packages30 form a top manifold and the outlets 16 form a bottom manifold, suchthat the fluid is evenly distributed in “parallel” fluid paths throughthe internal channel systems (formed by the apertures 26 shown in FIG.2) of each of the laser diode packages 30.

Electrical current flows between the bottom contact 48 and a respectivelaser diode bar of the top laser diode package 30 a. Specifically,electrical current flows on a path that is electrically isolated fromthe coolant fluid path. The ceramic material (e.g. LTCC or HTCC) used inthe sheets of the laser diode packages 30 a, 30 b acts as an electricalinsulator to prevent electrical current from flowing to the coolantfluid. The electrical path created by the combination of the metalliclayer (or layers) of each laser diode package 30 a, 30 b and the springs36 a, 36 b, 36 c conducts electrical current to each laser diode bar 32of the laser diode packages 30. For example, the current path followssequentially the following path: the bottom contact 48, metallic layerassociated with the bottom contact 48, the spring 36 c associated withthe bottom contact 48, the bottom surface of the bottom laser diodepackage 30 b, the metallic layer(s) associated with the bottom laserdiode package 30 b, the laser diode bar associated with bottom laserdiode package 30 b, the spring 36 b associated with the bottom laserdiode package 30 b, the bottom surface of the top laser diode package 30a, the metallic layer(s) associated with the top laser diode package 30a, the laser diode bar associated with top laser diode package 30 a, andthe spring 36 a associated with the top laser diode package 30 a. Thecurrent would then continue to any other laser diode packages 30,eventually leading to a top contact, similar to the bottom contact 48.

Accordingly, because the electrical path is electrically isolated fromthe coolant fluid path the laser diode packages 30 can use, for example,non-deionized water as a coolant fluid. Thus, the laser diode packages30 eliminate the need to use deionized water and provide a high coolingcapacity by using an electrically non-conductive material (e.g., LTCCand diamond) to route the coolant fluid. In contrast to standard copper(coefficient of thermal expansion (CTE) about 16×10⁻⁶/per ° C.)microchannel coolers, the laser diode packages 30 of the presentinvention also reduce stress on the respective laser diode bars 32 inoperation. This is due to the fact that the ceramic sheets 12 b-12 i ofLTCC (CTE about 6×10⁻⁶/per °0 C.) and a top sheet 12 a comprised ofdiamond (CTE about 1.5×10⁻⁶/per ° C.) or BeO (CTE about 8×10⁻⁶/per ° C.)have coefficients of thermal expansion that are closer to the galliumarsenide of the laser diode bar (CTE about 6×10⁻⁶/per ° C.) thanmicrochannel coolers comprised of copper.

While the present invention has been described with LTCC and HTCC, themicrochannel coolers can be comprised of glass materials, such aslow-temperature glasses. As used herein, “ceramic” should be understoodto mean the inclusion of these glasses. It is also possible to uses BeOor diamond for all of the sheets 12 a-12 i with metallized surfaces(e.g., gold) allowing those sheets to bond together, such as throughdiffusion bonding.

While the present invention has been described with reference to one ormore particular embodiments, those skilled in the art will recognizethat many changes may be made thereto without departing from the spiritand scope of the present invention. For example, the microchannel cooler10 can use a “serial” cooling path instead of the “parallel” flow path ,e.g., the laser diode array 40 uses a single path in which the coolantsequentially flows through each laser diode package 30. Each of theseembodiments and obvious variations thereof is contemplated as fallingwithin the spirit and scope of the claimed invention, which is set forthin the following claims.

1. A laser diode package comprising: a laser diode for convertingelectrical energy to optical energy; a cooler including an exposed sheetand a plurality of ceramic sheets, the exposed sheet being a materialthat is electrically non-conductive and having a coefficient of thermalconductivity greater than the plurality of ceramic sheets, the exposedsheet including a region for receiving the laser diode, the plurality ofceramic sheets being fused together and the exposed sheet being attachedto a top ceramic sheet of the plurality of ceramic sheets, the ceramicsheets being made of a material selected from the group consisting oflow temperature cofired ceramics and high temperature cofired ceramics,each of the ceramic sheets and the exposed sheet having an inlet holefor receiving a non-deionized coolant fluid from a cooling source and anoutlet hole for returning the coolant fluid to the cooling source, anumber of the ceramic sheets having one or more multi-directionalapertures for distributing the coolant fluid within the cooler in adirection that is transverse to the direction of the flow of the coolantfluid within the inlet hole, each of the multi-directional aperturesextending entirely through the thickness of the respective ceramicsheet, the multi-directional apertures including a firstmulti-directional aperture extending transversely away from the inlethole of one of the ceramic sheets, the multi-directional aperturesforming a thee-dimensional flow path through the plurality of ceramicsheets that directs the coolant fluid from the first multi-directionalaperture to the outlet hole, one ceramic sheet including a plurality ofperforations each of which is substantially smaller than the apertures,each of the plurality of perforations in the one ceramic sheet creatinga corresponding individual coolant stream that flows through the oneceramic sheet and impinges on a back surface of the exposed sheet withinthe laser-diode receiving region, the plurality of perforations creatinga turbulent flow adjacent to the back surface of the exposed sheet, thecoolant fluid returning in a direction toward the one ceramic sheetafter impinging on the exposed sheet; and a metallization layer on thecooler on at least the laser-diode receiving region of the the exposedsheet for conducting the electrical energy to the laser diode.
 2. Thelaser diode package of claim 1, wherein the exposed sheet is selectedfrom a group consisting of a BeO sheet and a diamond sheet.
 3. The laserdiode package of claim 1, wherein the plurality of perforations includesat least three perforations aligned in a first direction and at leastsix perforations aligned in a second direction to form an array of atleast 18 perforations.
 4. The laser diode package of claim 1, whereinthe metallization layer is selected from a group of materials consistingof gold, gold alloys, platinum, platinum alloys, nickel, and nickelalloys.
 5. The laser diode package of claim 1, wherein the metallizationlayer extends entirely around the cooler and is located on a bottomceramic sheet that opposes the exposed sheet.
 6. The laser diode packageof claim 1, further comprising an electrically non-conductive substrateadjacent to the laser diode for relieving stress when coupling the laserdiode package to a second laser diode package in an array of laser diodepackages.
 7. The laser diode package of claim 6, further comprising aspring connector connected to the laser diode and the substrate, thespring connector conducting electrical energy from the laser diode to asurface of the second laser diode package.
 8. The laser diode package ofclaim 7, in combination with the second laser diode package to form anarray of laser diode packages, the array including an alignment pinextending through openings in the laser diode packages for aligning thelaser diode packages.
 9. A method of manufacturing a laser diodepackage, comprising: providing a cooler comprised of a plurality ofbonded ceramic sheets and a thermally-conductive sheet, thethermally-conductive sheet being bonded to a top ceramic sheet of theplurality of ceramic sheets, the thermally-conductive sheet having ahigher coefficient of thermal conductivity than the plurality of ceramicsheets, each of the bonded ceramic sheets containing an inlet hole andone or more apertures, the apertures on adjacent ceramic sheetspartially overlapping to define a plurality of internal channels withinthe cooler, the plurality of internal channels creating athree-dimensional coolant flow path within the cooler that moves acoolant transversely away from the inlet holes, the coolant flow pathincluding a first portion that is in a direction perpendicular to andtoward the thermally-conductive sheet and a second portion that is in adirection perpendicular to and away from the thermally-conductive sheet,the first portion of the coolant flow path being defined by a pluralityof individual fluid streams created by an array of perforations withinone of the ceramic sheets, each of the perforations being smaller thanthe apertures, the array including a plurality of perforations alignedin a first direction and plurality of perforations aligned in a seconddirection, the plurality of individual fluid streams flowing through theplurality of perforations within the one of the ceramic sheets creatinga turbulent fluid-flow adjacent to the thermally-conductive sheet;applying a metallization layer to the thermally-conductive sheet; andattaching a laser diode to the metallization layer.
 10. The method ofclaim 9, wherein the thermally-conductive sheet is diamond.
 11. Themethod of claim 9, wherein the plurality of ceramic sheets is selectedfrom a group of materials consisting of a low-temperature cofiredceramic and a high-temperature cofired ceramic.
 12. The method of claim9, wherein the plurality of ceramic sheets are comprised of glass.
 13. Alaser diode package comprising: a laser diode for converting electricalenergy to optical energy; a cooler for receiving a coolant from acooling source, the cooler including internal channels for routing thecoolant against a laser-diode mounting region within an exposed sheet,the cooler comprised of a plurality of electrically non-conductivesheets being fused together and including a first sheet having a firstaperture and a second aperture, the first aperture being separate fromthe second aperture, each of the first aperture and the second aperturereceiving the coolant from a coolant inlet hole and distributing thecoolant within the cooler in a direction that is transverse to thedirection of fluid flow in the coolant inlet hole, and a second sheetadjacent to the first sheet and having a third aperture for distributingthe coolant in a direction that is transverse to the direction of fluidflow in the coolant inlet hole, the third aperture receiving the coolantfrom the first aperture and transmitting the coolant to the secondaperture, a stream-forming sheet that includes an array of perforationsforming a plurality of individual fluid-streams that flow through thestream-forming sheet and impinge on the laser-diode mounting region tocreate a turbulent flow adjacent to the laser-diode mounting region,each of the perforations being smaller than the first, second, and thirdapertures, and the exposed sheet having a higher thermal conductivitythan the plurality of sheets and being attached to a top sheet of theplurality of sheets; and a metallization layer on the laser-diodemounting region of the exposed sheet for conducting the electricalenergy to the laser diode.
 14. The laser diode package of claim 13,wherein the material of the plurality of sheets has a coefficient ofthermal expansion that is close to the coefficient of thermal expansionfor the material of the laser diode.
 15. The laser diode package ofclaim 13, wherein the plurality of sheets are made of a low-temperaturecofired ceramic.
 16. The laser diode package of claim 1, wherein thearray of perforations includes at least three perforations aligned in afirst direction and at least six perforations aligned in a seconddirection.
 17. The laser diode package of claim 1, wherein at least twosheets of the plurality of ceramic sheets include a plurality ofisolated multi-directional apertures, the isolated multi-directionalapertures being discontinuous from each other and from the inlet holeand the outlet hole.
 18. The laser diode package of claim 1, whereineach individual perforation of the array of perforations has a dimensionon the order of several hundred microns.
 19. A laser diode packagecomprising: a laser diode for converting electrical energy to opticalenergy; a cooler comprising a laser-diode mounting region within whichthe laser diode is mounted, a coolant inlet, a coolant outlet, and aplurality of ceramic sheets that are fused together, at least some ofthe ceramic sheets having one or more multi-directional aperturesextending entirely through the thickness of the respective ceramicsheet, the multi-directional apertures on adjacent ceramic sheetsoverlapping for forming a three- dimensional flow path within the coolerthat leads from the coolant inlet to the coolant outlet, thethree-dimensional flow path routing a coolant to the laser-diodemounting region, one of the ceramic sheets being a stream- forming sheetthat includes a plurality of perforations, the coolant flowing throughthe plurality of perforations in the stream-forming sheet to create aplurality of individual coolant streams directed toward the laser-diodemounting region, the plurality of perforations creating a turbulent flowadjacent to the laser-diode mounting region by forming the individualcoolant streams impinging on the laser-diode mounting region, thecoolant returning in a direction toward the stream-forming sheet afterimpinging on the laser-diode mounting region; and a metallic conductionpath on the cooler for conducting the electrical energy to the laserdiode.
 20. The laser diode package of claim 19, wherein the plurality ofceramic sheets are made of a low-temperature cofired ceramic.
 21. Thelaser diode package of claim 19, wherein a top sheet of the plurality ofceramic sheets is made of a material having a coefficient of thermalconductivity greater than the remaining ones of the ceramic sheets, thetop sheet including at least a portion of the laser-diode mountingregion.
 22. The laser diode package of claim 19, wherein the pluralityof perforations are provided in an array of perforations that includesat least three perforations aligned in a first direction and at leastsix perforations aligned in a second direction.
 23. The laser diodepackage of claim 19, wherein each of the perforations has a dimension onthe order of several hundred microns.